As abrasive tapes of the above stated kind, in general, there are those of a structural organization wherein, on a substrate material, a coating comprising a polishing abrasive material and a binder component is applied to form a polishing film. An abrasive tape of this character has a simple structural organization and can be readily produced. During its use, however, debris formed from the workpiece being polished tends to infiltrate between the abrasive polishing film of the abrasive tape and the workpiece. If the polishing process is continued in this state, the surface of the workpiece will be damaged by this polishing debris, or the polishing debris will adhere to the film surface and cause its pores or recesses to become clogged. As a result, the polishing capacity of the abrasive tape has dropped considerably heretofore.
Furthermore, an abrasive tape provided with grooves in its polishing layer has been proposed. In the process of forming the polishing layer of this tape, a paint containing a large quantity of an inorganic ingredient in a coating compound is applied. Then the concavities and convexities of the Bernard cell due a "convection cell phenomenon" which occurs in the coating layer at the time when the solvent is dried are utilized as groove forms of the polishing layer. (Reference: Japanese Pat. Laid-Open Publn. No. 62-255069.) In the case of this abrasive tape, however, the shape as viewed in plan view of the grooved parts thus formed becomes restricted to an approximately hexagonal shape for reasons due to the production method. Moreover, it has been difficult to form recesses consistently of the same pattern, and products of stable quality could not be easily obtained. Furthermore, the control of conditions such as the composition of the solvent of the coating material for forming the polishing layer, the coating quantity, and the drying conditions in the production process for uniformity and stabilization of the pattern of the grooved parts to be thus formed has been difficult. Consequently, there has been the problem of extremely complicated production procedures. Furthermore, the concavities and convexities that can be formed on this abrasive tape is limited, in terms of the number of the polishing abrasive, to between #6,000 and #7,000 measured according to JIS R 6001. Polishing abrasives of numbers higher than this (i.e., concavities and convexities of dimensions less than this) could not be obtained.
Furthermore, in the method described in the above mentioned Japanese Pat. Laid-Open Publn. No. 62-255069 and other known methods (Japanese Utility Model Laid-Open Publn. Nos. 55-89564 and 59-39168), the forming of polishing layers into concave-convex pattern forms by using a printing process such as gravure printing and screen printing is disclosed. Furthermore, in Japanese Pat. Laid-Open Publn. No. 2-83172, the forming of a concave/convex pattern by applying a coating of a resin liquid in which polishing abrasive particles have been dispersed on a film substrate and laminating thereon by pressing a film for imparting concavities/convexities is disclosed. By this method, it has not been possible to prevent completely the formation of projections of independent polishing abrasive material on the surface of the polishing layer thus obtained. When such projections are present, the workpiece undergoing polishing is damaged by scratching or scoring. Thus this method becomes unsuitable especially for polishing requiring precision.
Furthermore, because of friction between the abrasive tape and the workpiece being polished, the abrasive tape and the workpiece become electrostatically charged at the time of polishing. For this reason the removal of polishing debris from the polished parts becomes difficult, and residual polishing debris becomes entrapped between the abrasive tape and the workpiece, whereby scratch damage occurs, or dust in the air or polishing debris is adsorbed on the surface after polishing and must be subsequently cleaned off.
Furthermore, depending on the conditions, sparking may occur between the abrasive tape and the workpiece and damage the surface of the workpiece in some cases.
Accordingly, it is an object of the present invention to obtain an abrasive tape of high quality which is capable of solving the above described problems of the prior art.
It is another object of this invention to obtain a novel method by which the above described abrasive tape can be stably produced.